1. Field of the Invention
This invention relates to methods of analyzing biological specimens using biological micro-electromechanical systems (bioMEMs). The invention includes analysis methods and apparatus used as a microfluidic biosensor, optical resonator, and micro- and nanolaser device that measure optical properties of bioparticles including biological cells, organelles and molecules.
2. Description of the Prior Art
BioMEMs technologies derive from novel developments in materials and micro/nanofabrication methods. The prior art cited teach how to use these integrated technologies (e.g., microfluidics, electronics and photonics, and biocompatible surface chemistries) to create fluidic systems that are well suited to carry, manipulate, detect, analyze and process biological molecules, organelles, and whole cells. These systems also benefit from new light sources derived from semiconductors and solid state devices to enable efficient new tools for bioanalysis because they are small, easily integrated with microfluidics, and are well-adapted to microscopy and spectroscopy for imaging, flow spectrocytometry, and high speed analysis.
In prior art, U.S. Pat. No. 5,608,519 describes an apparatus and method for microscopic and spectroscopic analysis and processing of biological cells. The apparatus comprises a laser having an analysis region within the laser cavity for containing one or more biological cells to be analyzed. The presence of a cell within the analysis region in superposition with an activated portion of a gain medium of the laser acts to encode information about the cell upon the laser beam, the cell information being recoverable by an analysis means that preferably includes an array photodetector such as a CCD camera and a spectrometer. The apparatus and method may be used to analyze biomedical cells including blood cells and the like, and may include processing means for manipulating, sorting, or eradicating cells after analysis thereof.
The prior art describes a biocavity laser device developed for the analysis of whole cells in the geometrical optical regime a>>λ where the bioparticle radius a is much larger than the wavelength λ of the probe light wavelength. That prior art is limited in its scope since the preferred embodiment did not teach how to use optical cavities to analyze the full range of bioparticle sizes from the geometrical regime a>>λ, to the intermediate Mie regime a≈λ, to the Rayleigh limit a>>λ. Cells are typically 10 microns or larger and exhibit multimode lasing properties. Micrometer- and nanometer-sized bioparticles in a cavity exhibit single mode lasing or no bioparticle-supported lasing at all, and are subject to different optical physics. Further, the prior art did not teach methods on how to relate the measured optical properties of small bioparticles to a biomolecular composition, nor did it teach how statistical distributions of these optical properties change from a normal to an abnormal or disease state. The prior art did not teach how to make fluid grates within a cavity to enable very high-speed parallel processing of small bioparticles. Nor did it teach how the microfluidic velocity distribution is related to the geometry and dimensions of fluidic structures within the cavity. Thus, there was no teaching on how to locate an analysis region in a cavity to optimize the fidelity, robustness, counting rates, and measurements of single bioparticles. Further, FIG. 4 of the prior art describes a preferred embodiment using micromachined channels in a silicon substrate with an attached gain region. This has the disadvantage for study of small bioparticles that side-scattered light in the channels is less accessible due to absorption.